Conventionally, a secondary battery has been known that is configured of a plurality of battery cells that each include an electrolyte layer and a positive electrode and a negative electrode each disposed on a surface of the electrolyte layer and are stacked in layers with a collector plate posed therebetween, as proposed for example in Japanese Patent Laying-Open Nos. 2004-031255, 2004-095400, 2005-174691, 2005-050756 and 2005-011660.
Such a secondary battery is utilized as a storage battery, and an electrode reaction caused between the positive electrode and the negative electrode causes discharging.
Such a secondary battery as described above has an inner portion and an end portion which are different in heat radiation efficiency and the inner portion has a tendency to have higher temperature. As such, a battery cell located at the inner portion has an active electrode reaction and thus degrades faster, resulting in the secondary battery as a whole having a reduced life.
Furthermore, even if each battery cell is driven normally, it outputs a voltage that is not uniform, depending on the secondary battery's internal temperature distribution. Even if each battery cell's output voltage is sensed and a battery cell that deviates from a predetermined voltage can be detected, it is difficult to determine whether the deviation is attributed to that battery cell's defect or to temperature. Thus in the conventional secondary battery it is difficult to identify a defective battery cell.